Handheld pipettes are commonly used to dispense or transfer small but accurately measured quantities of liquids.
Air displacement pipettes are the most common variety of handheld pipettes. In an air displacement pipette, a controllable piston is mounted for movement axially within a chamber in the pipette; the piston moves in response to either manual control (as described above) or motorized electronic control. Typically, the piston moves in a chamber in the liquid end, or shaft, of the pipette, to which disposable pipette tips may be mounted.
An air tight seal is formed between the piston and the shaft. With such a seal in place, axial movement of the piston will vary the size of the airspace within the shaft. Moving the piston downward, into the shaft, will reduce the airspace and force air out of the shaft through an open distal end. Moving the piston upward, out of the shaft, will increase the airspace and cause air to be drawn into the shaft through the open end.
A disposable pipette tip is then sealed to the open distal end of the shaft. Then, as the piston is moved within the shaft, air—or a measured quantity of liquid equal in volume to the displaced air—is drawn into or forced out of the tip. With both the piston and the tip sealed to the shaft, the only entry and exit path should be the distal open end of the disposable pipette tip. Because of the sealed system, air displacement pipette may be used to make accurate and precise measurements, and to move carefully calibrated quantities of liquids.
To function properly, then, not only do air displacement pipettes require a reliable seal between the tip and the shaft, but they also require a seal between the shaft and the piston. There are two seals, and two potential points of failure. The seal between the tip and the shaft is replaced every time a tip is discarded and replaced with a new one, but the seal in the pipette is serviced infrequently. This may lead to leaks and other failures, which in turn may lead to inaccuracy in liquid measurement or failure in pipetting operations.
In general, seal failure (such as wear, splitting, other damage, misalignment, dislodgment, corrosion, or contamination) is a common cause of pipetting failure. These failures can lead to failed outcomes, and may be difficult to identify in advance, or even as pipetting is ongoing. Wear and damage to the shaft in the tip mount region can also result in failures, and for this reason, plastic pipette shafts are also replaced from time to time.
These problems may be mitigated to some extent by performing frequent calibrations and having pipette serviced relatively often. Best practices in this regard frequently involve regular seal replacement, even if it does not appear necessary. However, because a damaged or leaking seal may not be visually evident, and slightly inaccurate pipetting results may be attributed to numerous other causes (user error, environmental conditions, etc.) or overlooked entirely, some users may tend to skip required or recommended pipette services—especially because such services may take a needed pipette out of use at an inconvenient time.
Many organizations track the calibration and service status of their pipettes by maintaining centralized records that correlate pipettes' serial numbers (or other individually trackable information, like asset tag numbers) to a listing of calibration or service dates. When a pipette comes up for a recommended service, an asset manager for the organization may then use these centralized records to identify where the pipette is kept, then either remove the pipette from the laboratory for service (if the pipette can be found) or alert a laboratory manager that service is required. If the pipette is out of place or unable to be located, or if the laboratory personnel are uncooperative, the service or calibration opportunity may be missed or significantly delayed, leading to potentially inaccurate results.
Some organizations also associate calibration and service requirements directly with each pipette, for example by affixing a small label to the pipette bearing recommended calibration or service dates. However, this is not an ideal solution, as such small labels may be easily overlooked, or the labels themselves may be dislodged or damaged through repeated handling, cleaning, or autoclaving. Adhesive labels may also be disfavored in some especially sensitive laboratory environments.
With either of these systems—centralized tracking and individual labeling—there is no integrated, centralized way to both manage and oversee pipette service and calibration while also tracking pipettes while they are in use.
Accordingly, there is a need for a simple, easy to operate system to manage and track pipette calibration and service status. Such a system would be ideally situated in a laboratory or other area where the pipetting is performed, and would provide information about the calibration and service status of pipettes in use within the laboratory with little or no manual intervention. A system for providing such information may take the form of a pipette check station, or even more advantageously a pipette storage stand or rack incorporating such pipette check functionality. Such a pipette check station may also facilitate periodic calibration spot-checks and provide a simple interface allowing a user to access additional pipetting-related products and services. A pipette check station may also provide information to a centralized asset tracking system, allowing an organization to maintain records of pipette use, calibration, and service events.